The sodium (Na) and potassium (K) levels of hypotonically lysed HeLa cells and erythrocytes have been measured for cell suspensions normally incubated at 37 degrees C and subjected to a hyperthermic incubation. While the viability of the cells (as measured by dye uptake) does not change, the Na content of the HeLa cells increases by 80% and the K content decreases by more than 60% after one hour of incubation at a hyperthermal temperature. No definitive changes have been observed with erythrocytes subjected to similar treatments. Immediate activities include quantifying changes of Na and K within the cells when they are exposed to different temperatures and ionic environments. Investigations which will hopefully establish the relation between eventual cell death and the observed changes of ion content are also in progress. These include experiments to determine: (1) the extent of the recovery of the original ion content of the cells when they are returned to physiological temperature after hyperthermal incubation; (2) the effects of the incubation on ion-linked co-transports; and (3) the relationship between respiratory rate and ion content. Na and K fluxes are being measured during and after the hyperthermal incubation in order to elucidate the mechanism leading to the observed changes of intracellular ion level. The amount of K ion released by cells undergoing the hyperthermal incubation may be used to monitor the "exposure dose" to heat. The amount of K ion in the intercellular milieu or in the plasma can be easily and very accurately measured. The reproducibility and reliability of the method as an indicator of "heat damage" must be studied. The proposed research is designed to help answer this question.